1. Field of the Invention
The present invention relates to a silver halide photographic light-sensitive material, in particular, a silver halide photographic light-sensitive material used for a photomechanical process and a photographic light-sensitive material used for IC printed boards. The present invention also relates to a package comprising a stack of the photographic light-sensitive materials packaged with a packaging bag.
2. Description of the Background
It is the integrated circuits (ICs) that support the today's highly information-oriented society from the aspect of hardware. It can be said that ICs are used because of their characteristics such as high processing speed, high reliability, low power consumption, low price, high functionality, light weight and small size. Meanwhile, for photographic light-sensitive materials, for example, light-sensitive materials for making printing plates, especially those used for IC printed boards, high reliability is required, and they play an important role. For example, a circuit pattern is prepared with the aid of computer-aided design (CAD), and a photographic light-sensitive material is exposed in this pattern in a full scale or reduced scale, developed and fixed to prepare a negative. A copper plate (or copper foil) applied with a resist is exposed using this negative as a mask by contact exposure or projection exposure in a reduced size usually using a mercury lamp as a light source so that the resist should be chemically denatured by ultraviolet rays emitted by the mercury lamp. There are a negative type resist and a positive type resist. In the former type, a portion irradiated with ultraviolet rays is not dissolved and remains in the subsequent development step, and a portion not irradiated with ultraviolet rays is dissolved in a developer. The reverse is applied to the positive type resist. In the both cases, for use of a negative of photographic light-sensitive material as a mask in contact exposure or projection exposure in a reduced size on a copper plate (or copper foil) applied with a resist, reproducibility of the negative image on the photographic light-sensitive material (stability for the development) is important.
In photomechanical processes used in the field of graphic arts, used is a method in which photographic images of continuous tone are converted into so-called dot images in which variable image density is represented by sizes of dot areas, and such images are combined with photographed images of characters or line originals to produce printing plates. For silver halide photographic light-sensitive materials used for such a purpose, ultrahigh contrast photographic characteristic enabling clear distinction between image portions and non-image portions has been required in order to obtain favorable reproducibility of characters, line originals and dot images. Silver halide photographic light-sensitive materials having such an ultrahigh photographic characteristic have a characteristic that they shows higher density (higher practice density) compared with low contrast materials even when laser exposure is performed with exposure giving the same half tone percentage. Therefore, for use in IC printed boards, suitability of resist for exposure is markedly improved.
As a system responding to such a requirement, there has been known the so-called lithographic development method, in which a silver halide light-sensitive material comprising silver chlorobromide is treated with a hydroquinone developer having an extremely low effective concentration of sulfite ions to form images of high contrast. However, in this method, the developer is extremely unstable against oxidation by air since the sulfite ion concentration in the developer is extremely low, and therefore a lot of developer must be replenished in order to stably maintain the developer activity.
As image forming systems in which the instability of the image formation according to the lithographic development method is eliminated and light-sensitive materials are processed with a developer showing good storage stability to obtain ultrahigh contrast photographic characteristic, for example, the one described in U.S. Pat. No. 5,650,746 and so forth can be mentioned. These are systems in which a silver halide photographic light-sensitive material of surface latent image type containing a hydrazine derivative is processed with a developer containing hydropuinone/metol or hydroquinone/phenidone as main developing agents and 0.15 mol/l or more of sulfite preservative and having pH of 11.0 to 12.3 to form ultrahigh contrast negative images having a gamma of 10 or higher. According to these systems, photographic characteristics of ultrahigh contrast and high practice density can be obtained, and because sulfite can be added to the developer at a high concentration, stability of the developer to air oxidation is markedly improved compared with conventional lithographic developers.
In order to form sufficiently ultrahigh contrast images with use of a hydrazine derivative, it is necessary to perform processing with a developer having pH of 11 or higher, usually 11.5 or higher. Although it has become possible to increase the stability of the developer by use of a sulfite preservative at a high concentration, it is still necessary to use such a developer of high pH as described above in order to obtain ultrahigh contrast photographic images, and the developer is likely to suffer from air oxidation and hence instable even with the presence of the preservative. Therefore, various attempts have been made in order to realize ultrahigh contrast images with a lower pH to further improve stability of the developer.
For example, Japanese Patent Laid-open Publication (Kokai, henceforth referred to as “JP-A”) No. 8-272023 discloses a method of using a highly active hydrazine derivative and a nucleation accelerator in order to obtain ultrahigh contrast images of high practice density by using a developer having pH of less than 11.0. However, silver halide photographic light-sensitive materials used for such an image-forming system have problems concerning storage stability such as fluctuation of sensitivity and increase of fog during storage due to incorporated highly active compounds, and they are desired to be solved.
Further, one of the drawbacks of nucleating high contrast negative image systems using a highly active hydrazine derivative and a nucleation accelerator, of which improvement is desired, is occurrence of the unfavorable phenomenon, uneven processing, and it poses a problem in their use for photomechanical processes and IC printed boards. The uneven processing referred to herein means difference in the sizes of half tone dots or unevenness of line widths caused by uneven nip pressure of development rollers during development process observed in half tone dot images in which half tone dots should have the same areas and images of the same line widths. Because this phenomenon greatly affects finish of half tone and highlight of printed matter, or precision of wiring for use in IC printed boards, improvement thereof is strongly desired.
Meanwhile, when a circuit pattern is prepared with the aid of computer-aided design (CAD) and photographed on a photographic light-sensitive material, a plotter provided with an automatic transportation system is used. In the automatic transportation system, transportation troubles due to influences of lubricity, static electricity and to forth may often occur and greatly degrade the productivity. Therefore, improvement of such troubles is strongly desired.